Seed colorant

ABSTRACT

A seed colorant useful especially in coloring seeds to distinguish same from those to be used for foods is formed of an aqueous medium such as water, a dye and/or pigment of a desired hue, and a binder resin composed of the salt of chitosan and an organic acid. The seed colorant may additionally contain spherical resin particles.

This is a division of application Ser. No. 152,498, filed 2/5/88, nowU.S. Pat. No. 4,853,429.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a novel agent for coloring seeds (willhereinafter be called "seed colorant"), and more specifically to a novelseed colorant having excellent adhesion to various seeds and giving goodinfluence to the germination percentage and growth of the seeds.

(2) Description of the Prior Art

A variety of seeds such as cereals has heretofore been used in anenormous quantity for foods. Of these seeds, those to be used forseeding have been subjected to various disinfection and other chemicaltreatments. Their accidental use for foods is hence very dangerous. Inview of this, seeds to be used for seeding are often colored in varioushues so as to indicate clearly that they are for seeding.

Employed routinely as such seed colorants are those obtained by eitherdissolving or dispersing a dye and/or pigment in a solution of a binderresin. Regarding such a binder resin, an emulsified hydrophobic vinylresin or a water-soluble resin is used as a synthetic binder resin byway of example. In addition, natural water-soluble resins are also usedwidely.

The following properties are required for such binder resins. First ofall, they are not supposed to give any deleterious effects to seeds. Asa second requirement, they must have sufficient adhesion to seeds.

Where an emulsion of a hydrophobic synthetic resin is used as such abinder resin for seeds, it has good adhesion to the seeds. It howeverinvolves a potential danger of giving adverse effects to the germinationand growth of the seeds, because one or more monomers still remain inthe emulsion and a surfactant is also used in combination in theemulsion. It is also desirable that the binder resin would bebiodegraded promptly subsequent to seeding. Such a hydrophobic syntheticresin is however accompanied by a further drawback that it has poorbiodegradability.

On other hand, water-soluble synthetic binder resins such as polyvinylalcohol are free of such monomer- and surfactant-related problems.However, they are also accompanied by a drawback that theirbiodegradability is poor. Further, they are highly hygroscopic and aretherefore inferior in adhesion. They are accompanied by a furtherproblem that seeds are caused to get together since seed surfaces becomesticky as a result of absorption of moisture.

Further, water-soluble natural binder resins such as cellulosederivatives, gelatin and casein have superb biodegradability but similarto the above-mentioned resins, they are inferior in the adhesion toseeds and other properties.

As a coloring agent, it is preferable to use a pigment having excellentfastness. This pigment is however inferior in the stability of itsdispersion in a solution of such a binder resin, and therefore is notequipped sufficient stability as a coloring agent.

It has hence been desired to develop a novel seed colorant which doesnot have any adverse effects to seeds, can exhibit good adhesion to theseeds, has excellent biodegradability and is superb in the stability ofdispersion of its pigment or pigments.

SUMMARY OF THE INVENTION

The present inventors have carried out an extensive investigation with aview toward solving problems of the prior art such as those mentionedabove. As a result, the present invention has been completed.

In one aspect of this invention, there is thus provided a seed colorantcomprising an aqueous medium, a dye and/or pigment, and a binder resincomposed of the salt of chitosan and an organic acid. It should be bornein mind that the combined use of two or more salts of chitosan and thecorresponding number of organic acids of different kinds, for example,formic acid and acetic acid, also falls within the scope of thisinvention. Such salts may be prepared separately or may be formed atonce by reacting chitosan with two or more organic acids of differentkinds.

Owing to the use of the organic acid salt of chitosan as a binder resinin the seed colorant, the present invention has brought about thefollowing advantageous effects

(1) The seed colorant does not have any adverse effects to seeds, butforms colored coating films which show germination-promoting effects onthe contrary.

1 (2) The thus-formed colored coating films are composed mainly ofchitosan which is a natural product. The coating films can thereforefirmly adhere on the surfaces of seeds which have also occurrednaturally, and can successfully withstand friction caused by collisionsamong the colored seeds in the course of their transportation or thelike, so that the coating films exhibit superb adhesion.

(3) Since the principal component of the colored coating films thusformed is chitosan, the coating films show good biodegradability, andgive no deleterious effects to the germination and growth of The seedsbut rather promote their germination and growth.

(4) The organic acid salt of chitosan, which has already been formedinto coating films, becomes moistureproof owing to partial evaporationof the organic acid so that problems attributable to the absorption ofmoisture do not occur any longer.

(5) The dye and/or pigment has good dispersion stability, so that nosurfactant is required practically. The surfactant-related adverseeffects can hence be avoided.

When an acid dye is used as a dye in particular, chitosan and the aciddye form a salt to fix the acid dye. The acid dye is hence no longerdissolved out, thereby making it possible to avoid contamination of thesurrounding during storage or handling.

DETAILED DESCRIPTION OF THE INVENTION

The above and other objects, features and advantages of the presentinvention will become apparent from the following description of theinvention and the appended claims.

The aqueous medium useful in the seed colorant of this invention iscomposed principally of water. It may however additionally contain asmall amount of a water-soluble organic solvent, for example, an alcoholor glycol.

The dye and/or pigment useful in the practice of this invention arethose known to date. Any conventional dyes and/or pigments are usable inthe present invention. It is general to use such a dye and/or pigment ata total concentration of about 0.1-about 10 wt.% based on the aqueousmedium.

The term "chitosan" as used herein means a substance obtained bydeacetylating chitin which is contained in the integument of acrustacean such as crab, shrimp or lobster. Chitosan per se is a knownmaterial. Chitosan samples of various degrees of deacetylation andvarious molecular weights are readily available on the market and canalso be produced with ease.

These known chitosan samples are all usable in the present invention.

Any organic acid may be used as an organic acid for the formation of asalt with chitosan as described above, so long as it has a certaindegree of solubility in the aqueous medium. Illustrative examples of theorganic acid may include formic acid, acetic acid, carboxylic acid,citric acid, malic acid, lactic acid, hydroxymalonic acid, malonic acid,succinic acid, adipic acid, benzoic acid, salicylic acid, aminobenzoicacid, phthalic acid and vitamin C. Among these, particularly preferredare those occurring naturally, such as lactic acid, malic acid andcitric acid. As already mentioned above, two or more organic acids mayalso be used in combination.

The proportion of such an organic acid to be used relative to chitosanvaries depending on the degree of deacetylation of chitosan (in otherwords, the basicity of chitosan) and the equivalent number of the acid,and cannot be specified sweepingly. As a matter of fact, it is a valuewhich allows the resulting organic acid salt of chitosan to retainwater-solubility. In general, the proportion of the organic acid mayrange from about 0.8 to about 2 moles per mole of amino groups inchitosan.

It is preferable to use such an organic acid salt of chitosan at aconcentration of about 0.1-about 20 wt.% in the seed colorant of thisinvention. If it should be used too little, the strength of theresultant colored coating films will be insufficient. If it should beused too much, the viscosity of the resulting colorant will becomeexcessively high. It is therefore not preferable to use such an organicacid salt of chitosan at any concentrations outside the above range.When such an organic acid salt is used at a higher concentration, it ispreferable to use chitosan whose molecular weight is relatively low.

The seed colorant of this invention contains, as essential components,an aqueous medium, a dye and/or pigment and an organic acid salt ofchitosan, such as those described above respectively. In addition, otherwater-soluble polymer, surfactant, disinfectant, germination promoter,growth hormone, etc. may also be incorporated so long as their additiondoes not impair the objects of the present invention. In particular,addition of fine resin particles conventionally called "plastic pigment"as one of such additives, for example, fine particles of an acrylicresin, polyethylene resin, polyamide resin, melamine resin, epoxy resinor the like in an amount of 10-100 parts by weight per 100 parts byweight of the organic acid salt of chitosan is preferred, since thelubricity of the resulting colored coating films is improved, thewearing resistance of the colored coating films formed on the surfacesof seeds is enhanced, and still better adhesion is obtained accordingly.

The seed colorant of this invention can be easily obtained by mixing inan arbitrary order essential and optional components such as thosementioned above and where a pigment is used as a coloring agent, byadditionally processing the resultant mixture for the dispersion of thepigment.

The present invention will hereinafter be described more specifically bythe following Examples, in which all designations of "part", "parts" and"%" mean part by weight, parts by weight and wt.% unless otherwisespecifically indicated.

EXAMPLE 1

An aqueous solution (viscosity: 5 cps at 25° C.) of a salt of lacticacid and chitosan was prepared (concentration of chitosan 1%;concentration of lactic acid: 1%). The solution was divided into threeequal portions, to which Pigment Green 7, Pigment Green 128 and PigmentRed 122 were added respectively to a concentration of 2.5%. Theresultant mixtures were separately processed for the dispersion of thepigments, thereby obtaining three seed colorants of different colorsaccording to the present invention.

Three 100-g portions of seeds for radish sprouts ("2MAMINA", trade mark)were sprayed respectively with 4 g of the three seed colorants of thedifferent colors according to this invention. After mixing the portionsof the seeds separately and thoroughly, they were dried separately.

The thus-obtained three seed samples of the different colors wereseparately placed in plastic bags and were strongly shaken up and downfor 5 minutes. None of the seed samples developed any substantialseparation of their colored coating films

In addition, a germination test was conducted on each of the coloredseed samples. The germination and growth were by no means inferior tothose of its corresponding uncolored seeds but on the contrary, evensome improvements were observed.

EXAMPLE 2

The procedure of Example 1 was repeated except for the use of citricacid as an organic acid. Good results were obtained like Example 1.

EXAMPLE 3

The procedure of Example 1 was repeated except for the use of malic acidas an organic acid. Good results were obtained like Example 1.

EXAMPLE 4

The procedure of Example 1 was repeated except for the use of a red aciddye (concentration: 0.5%) instead of the pigments. Good results wereobtained

like Example 1.

EXAMPLE 5

The procedure of Example 1 was repeated except for the additional use ofspherical polymethacrylate resin particles ("MP-1000", trade name:product of Soken Chemical & Engineering Co., Ltd.) in an amount one halfof the pigments. Good results were obtained like Example 1.

We claim:
 1. Seeds colored with a colorant comprising:an aqueous medium;a dye and/or pigment; and a binder resin composed of the salt ofchitosan and an organic acid.
 2. The seeds as claimed in claim 1,wherein the organic acid is selected from the group consisting of formicacid, acetic acid, propionic acid, butyric acid, taurine,pyrrolidonecarboxylic acid, citric acid, malic acid, lactic acid,hydroxymalonic acid, malonic acid, succinic acid, adipic acid, benzoicacid, salicylic acid, aminobenzoic acid, phthalic acid and vitamin C. 3.The seeds as claimed in claim 1, where the organic acid is anaturally-occurring organic acid.
 4. The seeds as claimed in claim 3,wherein the naturally-occurring organic acid is lactic acid, malic acidor citric acid.
 5. The seeds as claimed in claim 1, wherein the dyeand/or pigment is contained at a total concentration of 0.1 - 10 wt.% ofthe aqueous medium.
 6. The seeds as claimed in claim 1, wherein the salthas been formed by using the organic acid in an amount of 0.8 - 2 molesper mole of amino groups in the chitosan.
 7. The seeds as claimed inclaim 1, wherein the proportion of the salt is 0.1 - 20 wt.% based onthe seed colorant.
 8. The seed as claimed in claim 1, further comprisingspherical resin particles.
 9. The seeds as claimed in claim 8, wherein10 - 100 parts by weight of the spherical resin particles are containedper 100 parts by weight of the salt.
 10. The seeds colorant as claimedin claim 8, wherein the spherical resin particles are made of an acrylicresin, polyethylene resin, polyamide resin, melamine resin or epoxyresin.